[Vision2020] Mole Day 10-23 between 6.02 am & pm

[Kenneth Marcy]

I hope everyone had a pleasant Pi day yesterday, 3-14.

Another science holiday to note is Mole day, 10-23, between 6.02 in 
the morning and evening. The reference for Mole day is to a chemical 
constant, Avogadro's number, 6.02 x 10^23, which is a number of 
formula units. The term mole, like a dozen or a gross, refers to a 
particular number of things. A dozen eggs equals 12 eggs, a gross of 
pencils equals 144 pencils, and a mole of ethanol equals 6.02 x 10^23 
ethanol molecules.

From where did the mole concept come? A German chemist named Ostwald 
around 1900 suggested that the term mole [sic] be applied to the 
number of molecules [Avogadro's number] of an ideal gas at standard 
temperature and pressure in a volume of 22414 milliliters. Since 
Ostwald's time, a mole has been redefined as the number of atoms of 
carbon-12 in exactly 12 grams of carbon-12, which, experimentally, 
yields the same Avogadro's number. 

If you weighed a dozen small eggs, then added their weights, that sum 
would be less than the sum of the weights of a dozen larger eggs. 
Analogously, the weight (i.e., the mass) of an Avogadro's number of 
carbon atoms, with atomic number of 12, will be less than the mass of 
an Avogadro's number of oxygen atoms, with atomic number of 16.

A molecule of oxygen has two atoms of oxygen bonded together. So, a 
mole of oxygen will have twice as many atoms of oxygen as it will 
have molecules of oxygen. The molar mass of a substance is the mass 
of an Avogadro's number of molecules of it. Oxygen gas's molar mass 
is 32, comprised of two oxygen atoms of atomic number 16. Ethanol, 
comprised of two carbons, one oxygen, and six hydrogens, has a molar 
mass of 46.1.

So, there's a little chemistry to look forward to October 23, which is 
a Friday this year. It may be a nice time to remember, and to thank, 
your chemistry teacher. (Mine is still alive, in retirement.) You 
could use your greeting-card-making software to make a Mole Day card, 
and then mail it to your teacher. Imagine a shock, then the pleasure.


Ken